<template>
  <div class="container">
    <!-- 固定导航 -->
    <van-nav-bar
      fixed
      left-arrow
      @click-left="$router.back()"
      title="小思同学"
    ></van-nav-bar>

    <!-- 聊天主体区域 -->
    <div class="chat-list">
      <div v-for="(obj, index) in list" :key="index">
        <!-- 左侧是机器人小思 -->
        <div class="chat-item left" v-if="obj.name === 'xs'">
          <van-image
            fit="cover"
            round
            src="https://img.yzcdn.cn/vant/cat.jpeg"
          />
          <div class="chat-pao">{{ obj.msg }}</div>
        </div>

        <!-- 右侧是当前用户 -->
        <div class="chat-item right" v-else>
          <div class="chat-pao">{{ obj.msg }}</div>
          <van-image fit="cover" round :src="$store.state.userPhoto" />
        </div>
      </div>
    </div>

    <!-- 对话区域 -->
    <div class="reply-container van-hairline--top">
      <van-field placeholder="说点什么..." v-model="word">
        <template #button>
          <span style="font-size: 12px; color: #999" @click="sendFn">提交</span>
        </template>
      </van-field>
    </div>
  </div>
</template>

<script>
import { io } from "socket.io-client";
import { getToken } from "@/utils/token";

export default {
  name: "Chat",
  data() {
    return {
      word: "", // 输入框的内容
      // 所有的聊天消息
      list: [
        // 只根据 name 属性，即可判断出这个消息应该渲染到左侧还是右侧
        { name: "xs", msg: "hi，你好！我是小思" },
        { name: "me", msg: "我是编程小王子" },
      ],
      socket: null,
    };
  },
  created() {
    // 1.创建客户端 websocket 的实例
    this.socket = io("http://geek.itheima.net", {
      query: {
        token: getToken(),
      },
      transports: ["websocket"],
    });

    // 2.建立连接的事件
    this.socket.on("connect", () => {
      console.log("与服务器建立了连接");
    });

    // 3.接收到消息的事件
    this.socket.on("message", (data) => {
      // 把服务器发送过来的消息，存储到 list 数组中
      this.list.push({
        name: "xs",
        msg: data.msg,
      });
    });
  },

  methods: {
    // 向服务端发送消息
    sendFn() {
      // 判断内容是否为空
      if (!this.word) return;

      // 添加聊天消息到 list 列表中
      this.list.push({
        name: "me",
        msg: this.word,
      });

      // 把消息发送给 websocket 服务器
      this.socket.emit("message", {
        msg: this.word,
        timestamp: new Date().getTime(),
      });

      // 清空文本框的内容
      this.word = "";
    },
  },

  watch: {
    //监听list是否发生改变，让聊天信息自动滚动在屏幕上
    list: {
      handler() {
        this.$nextTick(() => {
          const theDiv = document.querySelector(".chat-list>div:last-child");
          theDiv.scrollIntoView({ behavior: "smooth" });
        });
      },
    },
  },
  // 组件被销毁之前，清空 sock 对象
  beforeDestroy() {
    // 关闭连接
    this.socket.close();

    // 销毁 websocket 实例对象
    this.socket = null;
  },
};
</script>

<style lang="less" scoped>
.container {
  height: 100%;
  width: 100%;
  position: absolute;
  left: 0;
  top: 0;
  box-sizing: border-box;
  background: #fafafa;
  padding: 46px 0 50px 0;
  .chat-list {
    height: 100%;
    overflow-y: scroll;
    .chat-item {
      padding: 10px;
      .van-image {
        vertical-align: top;
        width: 40px;
        height: 40px;
      }
      .chat-pao {
        vertical-align: top;
        display: inline-block;
        min-width: 40px;
        max-width: 70%;
        min-height: 40px;
        line-height: 38px;
        border: 0.5px solid #c2d9ea;
        border-radius: 4px;
        position: relative;
        padding: 0 10px;
        background-color: #e0effb;
        word-break: break-all;
        font-size: 14px;
        color: #333;
        &::before {
          content: "";
          width: 10px;
          height: 10px;
          position: absolute;
          top: 12px;
          border-top: 0.5px solid #c2d9ea;
          border-right: 0.5px solid #c2d9ea;
          background: #e0effb;
        }
      }
    }
  }
}
.chat-item.right {
  text-align: right;
  .chat-pao {
    margin-left: 0;
    margin-right: 15px;
    &::before {
      right: -6px;
      transform: rotate(45deg);
    }
  }
}
.chat-item.left {
  text-align: left;
  .chat-pao {
    margin-left: 15px;
    margin-right: 0;
    &::before {
      left: -5px;
      transform: rotate(-135deg);
    }
  }
}
.reply-container {
  position: fixed;
  left: 0;
  bottom: 0;
  height: 44px;
  width: 100%;
  background: #f5f5f5;
  z-index: 9999;
}
</style>
